The 375 Plus was developed as a successor to the 375 MM. While it shared the 2,600 mm wheelbase of its predecessor, it utilized a new type 505 chassis constructed of elliptical-section steel tubes. The primary mechanical advancement was the introduction of a de Dion axle at the rear, supported by twin radius arms, transverse leaf springs, and Houdaille shock absorbers. This configuration replaced the live axle and semi-elliptical springs of previous models, resulting in improved balance and road-holding.
The vehicle debuted in early 1954 but faced initial reliability issues, failing to finish both the Giro di Sicilia and the Mille Miglia.
The 1954 season served as the definitive competitive period for the 375 Plus. At the 24 Hours of Le Mans, the pairing of José Froilán González and Maurice Trintignant drove the 375 Plus to victory, marking Ferrari's first win at the event since 1949. The car finished ahead of the works Jaguar D-type. Further international success followed with victories at the Agadir GP and the Silverstone International.
The car's most significant individual performance occurred at the 1954 Carrera Panamericana, where Umberto Maglioli secured a victory that clinched the World Sportscar Championship for Ferrari. This proved to be the final running of the Mexican road race, as it was cancelled the following year. The 375 Plus remained competitive into 1955, taking a final major victory at the 1000 km Buenos Aires, though the remainder of that season's World Sportscar Championship was dominated by the Mercedes-Benz 300 SLR.
The 375 Plus was powered by the tipo 113 Lampredi V12 engine. To achieve a displacement of 4,954.34 cc, Ferrari engineers combined the 84 mm bore of the 375 MM with the 74.5 mm stroke from the 375 Formula One engine. The powerplant featured a single camshaft per cylinder bank, a single spark plug per cylinder, and two magnetos. Fuel was delivered via three Weber 46DCF/3 carburettors.
Most units produced 330 PS (243 kW; 325 hp) at 6000 rpm, with some engines reaching 345 PS, allowing for a top speed of 280 km/h. The 375 Plus utilized dry sump lubrication and a 4-speed or 5-speed manual gearbox mounted en bloc with the differential. To support long-distance endurance racing, the car was equipped with a 190-litre fuel tank, which necessitated a distinct rear bodywork bulge compared to the earlier Pinin Farina Spyder style.
The 375 Plus saw extensive use in North and South American regional racing. Between 1957 and 1958, Dan Gurney campaigned the model, scoring victories at Paramount Ranch and Palm Springs. Gurney also drove a 375 Plus to a second-place finish at the 1958 Grand Prix Riverside, which was part of the United States Grand Prix for Sports Cars.
While almost all examples were competition Spyders, one unique road-going variant exists. Chassis s/n 0488AM is a one-off, two-seater Cabriolet commissioned by King Leopold III of Belgium. Completed by Pinin Farina in 1955, this left-hand drive gran tourer featured covered headlamps and an unusually wide front grille. Originally finished in black with an ivory leather interior, it was later repainted red.
The 375 Plus is characterized by low production numbers and a high survival rate among significant chassis. Chassis s/n 0384AM, a former works car that competed at the Mille Miglia, Le Mans, and Silverstone, was sold at the 2014 Bonhams Goodwood Festival of Speed Sale for £10.7 million. Another notable example, chassis s/n 0398TF, has been part of the Ralph Lauren Collection since 1990. Additionally, chassis s/n 0478AM exists as a unique variant, having been converted from a 375 MM and rebodied by Sutton.